Matched getter



P 1965 M. B. FARRAR ETAL 3,207,294

MATCHED GETTER Filed Jan. 23, 1962 INVENTORS MILLARD B-FARRAR CLAIR W.REASH DWIGHT N.WAIT

United States Patent 3,207,294 MATCHED GE'ITER Millard B. Farrar, RockyRiver, Clair W. Reash, Fairview Park, and Dwight N. Wait, Rocky River,Ohio, assignors to Union Carbide Corporation, a corporation of New YorkFiled Jan. 23, 1962, Ser. No. 168,168 2 Claims. (CL 206-.4)

This invention relates to matched getters for use in the manufacture ofelectronic vacuum tubes, and to a method for their production. By use ofthe term matched getters applicants mean getters each of whose totalweight is maintained or controlled to be a uniform predetermined amount.

In the manufacture of electronic vacuum tubes, such as radio andtelevision tubes, it is necessary that the residual gases left in theevacuated tubes be removed in order to maintain high tube quality. Thesegases are customarily removed by use of a so-called getter which isincorporated into the tubes before they have been evacuated. The getterbriefly consists of a metallic container which is loaded with a powderedmetal, usually an alkaline earth metal, for example barium and calcium,which when vaporized has the ability to absorb the residual gases andremove them from the tubes. The getter is activated or flashed byheating it to a high temperature, suitably by induction heating,whereupon the metal is vaporized. While the amount of metal to bevaporized, that is, the getter yield, will most often depend on the typeof vacuum tube in which the getter is to be incorporated, the getter ina particular instance is required to satisfy a rigid standard ofuniformity in its yield. This standard must be satisfied because, whenthe getter yield is low, the vaporized metal will not completely removethe residual gases and, when the getter yield is too high, vaporizedmetal has a tendency to condense on the vital components of the vacuumtube, hence reducing its quality. Heretofore this standard has not beensatisfactorily met and, particularly when produced on a large scale,many getters of the type described have exhibited non-uniformity intheir yields.

According to the invention it has been discovered that an importantfactor in the production of getters having a uniform yield is the totalmass of the getter, that is, the combined weight of the container andpowdered metal, and that the total getter mass should be kept constant.The getter container is relatively small and because of its size, it isdiflicult to control its weight so that variations, however small, inthe size of the container result in getters whose yield is not uniform.However, it has been found in accord with the invention that when theweight of the powdered metal is adjusted to match the total weight ofthe getter to a production standard, getters can be made which exhibit aconsistently uniform yield when flashed.

The principal object of this invention therefore is to provide a matchedgetter which will satisfy the rigid standards required by manufacturersof vacuum tubes, and to provide a method for its production.

The invention will be described in greater detail by reference to theaccompanying drawing wherein the single figure is a partially sectionedelevational view of a getter embodying the principles of the invention.

Referring to the drawing there is illustrated a matched getter having asupport arm 10 secured to a container 12 of the channel ring type. Thecontainer 12 is loaded with a powdered metal 14 to be vaporized and issecured to the support arm 10 by two projection welds 16. The powderedmetal 14 may suitably be an alkaline earth metal, for instance, bariumor calcium. In the instance of the alkaline earth metal, however, whichmay be unstable in air, the metal is preferably alloyed with astabilizing metal such as aluminum.

In accord with the invention the weight of the powdered metal isadjusted so as to match the total weight of the getter to a productionstandard. This standard, of course, will depend on the particular typeof vacuum tube in which the getter is to be incorporated, but in anycase, the total weight of the getter should be suflicient to promote thevaporization of the required amount of metal to absorb the residualgases and remove them from the evacuated tube.

A number of matched getters of the construction illustrated andembodying the invention have been made and tested. For example, in onetest, getters were made in accord with the invention wherein the weightof the containers used was greater than a specified control because ofincreased thickness. Specifically, the getters were constructed of astainless steel container of the channel ring type approximately 18 mm.in diameter, wherein the channel measured about 0.06 inch wide by 0.107inch high. A powdered alloy was metered into the container, the weightof powder in each particular instance being suflicient to match thetotal weight of the getter to the weight of the control, and was thenpressed under a pressure of about 8000 pounds per square inch. Thepowdered alloy had a composition of 53% by weight of barium and 47% byweight of aluminum. The getters were then flashed in an evacuated 500ml. spherical flask. In each instance, the getter tested was located inthe neck of the flask on a spring support in the center of a 4 turn RF(radio frequency) induction coil. The flask was then evacuated and whenthe pressure reached 7 10- mm. of Hg or lower, the container was heatedby the coil to 1100 C. in about 12 seconds, at which time the bariumbegan to vaporize. The container was heated for a total of 25 seconds tocomplete the vaporization. After the test, the barium yield wascalculated and was recorded. In another test, getters of the identicalconstruction were made, but in this instance, the weight of the powderwas not adjusted. In still another test, the container weight wasvaried, while the Weight of powder was held constant. These getters weretested as described above, and their barium yields were calculated andrecorded. The results of these tests are tabulated in the table below,wherein the values listed are average values.

Barium yield vs. container and powder weight It will be appreciated fromthe above tabulated results that the matched getters of the inventionhad an average yield which closely approximated that of the controlgetter, and that when the powdered metal was not adjusted, the gettersexhibited a yield which was not uniform.

We claim:

1. A method formanufacturing getters having uniform, predeterminedyields upon flashing despite variations in the weight of the gettercontainers, wherein each of said getters comprises a quantity ofpowdered getter metal and a container therefor, comprising adjusting thetotal weight of each getter to be equal to a predetermined amount.

2. A getter comprising a quantity of powdered getter metal and acontainer therefor, having a predetermined yield upon flashingregardless of the weight of said con- 2,524,000 9/50 Spencer 252-181.7 X2,915,386 12/59 Strauss.

FOREIGN PATENTS 738,485 10/55 Great Britain.

THERON E. CONDON, Primary Examiner.

EARLE J. DRUMMOND, JOSEPH R. LIBERMAN,

Examiners.

2. A GETTER COMPRISING A QUANTITY OF POWERED GETTER METAL AND ACONTAINER THEREFOR, HAVING A PREDETERMINED YIELD UPON FLASHINGREGARDLESS OF THE WEIGHT OF SAID CONTAINER, WHEREIN SAID PREDETERMINEDYIELD IS ACHIEVED BY ADJUSTING THE TOTAL WEIGHT OF THE GETTER TO BEEQUAL TO A PREDETERMINED AMOUNT.